如图,矩形ABCD中,AB=8,点E是AD上的一点,有AE=4,BE的垂直平分线交BC的延长线于点F,连结EF交CD于点G.若G是CD的中点,则BC的长是( )
A:7
B:8
C:9
D:10
圆周长C与圆的半径r之间的关系为C=2πr,其中变量是____ ,常量是____ .
I got on the bus and found a seat near the back, and then I noticed a man ____ (sit) at the front.